Every company on the web is tracking each of its users and user behavior. Facebook, on the other hand, harvests user data more than anything. In relation to the fiasco of Cambridge Analytica, more companies were brought forward who share user data with other companies for massive profits. Due to this, GDPR came into the picture. Facebook also became more clear & also has come forward with the issue of its tracking and personalized advertising.
If you use an ad-blocker, you will see the number of websites that track your every move and the quantity of trackers every website throws at you. (They are literally coming to get you).
You can Stop Facebook Tracking of apps and websites up to a good number by turning off “Platform”. (It was earlier termed as “Platform”, now it is called just “Apps & Websites”.
Go to Settings. Click on Apps & Websites on the left sidebar. Look for the same option under preferences. Now Click on “Turn Off”.
Although this does not promise complete privacy, this is the least you can do. You can also use ad blockers, Remove connected apps completely from the Facebook platform.